CMMG .22LR evolution conversion, this happened yesterday:
Essentially, the back half of the .22LR casing was ripped off and the case fell out of the chamber about half as tall.
Is that a problem I should be worried about?
No I have not seen that malfunction. Was it a spent case that split?
It fired then ripped the case in two then smashed it when the bolt came forward?
The great picture
From what I recall, that was the last round in the mag, and I felt something was wrong, like it sounded different. I wish I knew where the case was, but when I got it out, the bullet and powder were all gone. Pretty sure a failure to extract or something, then the bolt hold open didn’t work.
Never had that happen…did it function properly after that?
I don’t know, after that round I switched back to 5.56. 
Well definitely let us know if it works next time!
I have had my conversion smash up the cases pretty good but can’t recall anything specific.
It looks like an out of battery discharge. The bolt doesn’t go all the way forward and the case isn’t fully supported by the chamber. It will blow out and shorten the case.
I’ve never had one with a .22 conversion kit but they do happen.
Here is an OOB discharge I had on a 9mm SMG:
Dude, I had the same thing happen to me with my 9mm MPA/MAC 11 Clone.
Our shells look darn near identical.
They do look like twins, don’t they? I think mine happened with an SWD M11/9 but I can’t remember for sure. It’s been too many years.
Did you check the bore to make sure the bullet is not stuck in there?
You beat me to it…I was thinking of Brandon Lee…an ideal squib moment. Dirty chamber + bad feed from last round + bad angle on the bolt and…bang…out of chamber .22 ignition. I’ve had Marlins do this, but not 10/22s - I think the Ruger rotary feed reduces chances of this happening.
Try another mag - or if you have a dummy 22 put in as the last round on a full mag and see if it stovepipes (once you have cleared barrel and cleaned chamber, bolt and extractor).
I see that is an Adams Arms upper. What position do you run the key in after you remove the rod?
I did, no round was in the barrel.
And the conversion is the cmmg evolution, which can be run with the Adams arms piston still installed. I tried running it with the gas port turned off once, and it made it extremely hard to turn it back on. I had to run about 8 5.56 rounds by manually charging the weapon after each shot to either clear out the fouling/carbon or to heat it up enough to turn it back to the normal gas setting.
It works on the normal gas setting, so don’t change anything, just swap bcgs and mags (and ch and bolt hold open thing if you want) and you’re good to go.
This is probably the problem, I just found the .22 casing in my bag and it looks pretty close to that. I’ll post a picture tomorrow.
Thanks for the advise. I will have to to get a cmmg evolution and dump the kit I have…
I had something like this happen back when I was shooting 7.62x51 NATO rounds out of my DPMS LR-308 that was chambered tightly for .308 match ammo. Anyhow, I had no problems with feeding, but instead I had issues with extraction. The casings got stuck in the chamber and when I extracted them I would shred the brass. It turned out that the tight tolerances resulted in the extraction issues and I had a gunsmith polish the feed ramps which allowed for smoother cycling of NATO rounds, which had thicker cases. Well, this may not have anything to do related to your problem, but I just thought I share my brash shaving experience. For all I know, there could be something in common with your problem.
I’ve had a Ruger 10-22 fire out of battery and do that. only had some fail to feed on the one I’ve got though. "Spikes W/ 22 LR barrel.